Sanitary earthen products

ABSTRACT

Disclosed is a sanitary ware which has a self-cleaning function for releasing carboxyl-containing greasy stains or soils, such as fatty acids, fatty esters, metallic soaps (scum of soaps), proteins, amino acids, bacteria, and fungi, and deposited stains or soils, such as water scale and urinary calculi. This sanitary ware comprises at least a sanitary ware body and a glaze layer as an outermost layer of the sanitary ware, a monovalent metal component and/or a metal component having a measure of the electronegativity based on Pouling&#39;s rule of not more than 1 being provided so as to be releasable evenly and continuously, over the whole surface of the glaze layer as the outermost layer, in such an amount large enough to impart a self-cleaning function for releasing stains or soils to the surface of the glaze layer as the outermost layer, the metal component being suppliable from the glaze layer as the outermost layer and/or the sanitary ware body to the whole surface of the outermost layer. The sanitary ware is advantageous in that stains or soils on the sanitary ware can be simply removed, for example, by running water without using any surfactant and without strongly scrubbing the surface of the sanitary ware by a scrubbing brush or a cleaning brush.

This application claims the benefit of International Application No.PCT/JP99/06621, which has the international filing date of Nov. 26,1999, and which was not published under PCT Article 21(2) in English.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to sanitary wares, such as toilets,urinals, strainers for urinals, flush tanks for toilets or urinals,washbowls in washstands, or wash hand basins.

2. Background Art

Good appearance and high cleanness are important for the surface ofsanitary wares from the viewpoints of hygiene and aesthetic effect.Further, retention of good appearance and high cleanness for a longperiod of time is preferred.

In order to keep the surface of sanitary wares clean and to retain goodappearance of the surface of sanitary wares, it is a common practice tostrongly scrub the surface thereof by a scrubbing brush or a cleaningbrush containing a detergent, such as a surfactant, an acid detergent,or an alkali detergent. Specifically, stains or soils deposited on thesurface of sanitary wares are removed through utilization of chemicaldetergency derived from the detergent and through utilization ofphysical cleaning action by scrubbing with the scrubbing brush or thecleaning brush.

This cleaning work is not light, and, hence, reducing the frequency ofthe cleaning work is desired. Further, in recent years, environmentalpollution by surfactant-containing wastewater has been pointed out.Therefore, reducing the amount of the surfactant used and the frequencyof use of the surfactant is desired.

Under these circumstances, several proposals have been made on sanitarywares having a surface that is highly hygienic and has good appearance.

For example, coating of a fluororesin or a siloxane resin containingfluoroalkyl groups onto the surface of sanitary ware has been proposedto lower the surface energy, thereby permitting stains or soils to beless likely to be deposited onto the surface.

Another proposal is such that the surface of sanitary ware is madesmooth as much as possible to prevent stains or soils from beingdeposited and strongly adhered onto the surface thereof. In thisproposal, however, the relationship of the surface state to theinhibition of deposition of stains or soils, fastness, and glossinesshas not been fully studied. Specifically, the sanitary ware having asmooth surface has been proposed based on such mere conceptualunderstanding that a smooth surface would inhibit the deposition ofstains or soils thereon and would be preferred from the viewpoint ofaesthetic effect.

Further, in connection with the antimicrobial activity of the surface ofthe sanitary ware, the following techniques have been proposed forimproving the glaze layer as the surface layer.

Japanese Patent Laid-Open No. 236846/1998 discloses a pottery or ceramicwhiteware product which has been prepared by applying, before firing, atransparent glaze with an inorganic antimicrobial agent incorporatedtherein onto a conventional color glaze and then firing the color glazeand the transparent glaze.

WO 96/23412 discloses a base glaze for a glaze layer to be provided onthe surface of an antimicrobial member. The base glaze for the glazelayer is prepared by mixing water, a material for a glaze, and a pigmenttogether, grinding the mixture to prepare a base glaze, mixing the baseglaze with a heat-resistant powder bearing an antimicrobial metal, andthen mixing the mixture with a binder.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sanitary warewhich permits stains or soils deposited on the surface thereof to besimply removed, for example, by running water.

The above object can be attained by the following invention.Specifically, according to the first embodiment of the presentinvention, there is provided a sanitary ware comprising at least asanitary ware body and a glaze layer as an outermost layer of thesanitary ware, a monovalent metal component and/or a metal componenthaving a measure of the electronegativity based on Pouling's rule of notmore than 1 (hereinafter referred to as a “cleaning metal component”)being provided so as to be releasable evenly and continuously, over thewhole surface of the glaze layer as the outermost layer, in such anamount large enough to impart a self-cleaning function for releasingstains or soils to the surface of the glaze layer as the outermostlayer, the metal component being suppliable from the glaze layer as theoutermost layer and/or the sanitary ware body to the whole surface ofthe glaze layer as the outermost layer.

According to the second embodiment of the present invention, there isprovided a sanitary ware wherein, in the sanitary ware according to thefirst embodiment of the present invention, the glaze layer as theoutermost layer is a transparent glaze layer and the sanitary warefurther comprises a colored glaze layer as an intermediate layerprovided between the sanitary ware body and the glaze layer as theoutermost layer.

According to the third embodiment of the present invention, there isprovided a sanitary ware wherein the sanitary ware according to thefirst embodiment of the present invention further comprises a metalcomponent layer which comprises the metal component as a main component,provided between the sanitary ware body and the glaze layer as theoutermost layer, the metal component being suppliable from the metalcomponent layer over the whole surface of the glaze layer as theoutermost layer.

According to the fourth embodiment of the present invention, there isprovided a sanitary ware wherein, in the sanitary ware according to thefirst embodiment of the present invention, the glaze layer as theoutermost layer is a transparent glaze layer and the sanitary warefurther comprises, provided between the sanitary ware body and the glazelayer as the outermost layer, a colored glaze layer as an intermediatelayer provided on the sanitary ware body side and a metal componentlayer which comprises the metal component as a main component, providedon the side of the glaze layer as the outermost layer, the metalcomponent being suppliable from the metal component layer over the wholesurface of the glaze layer as the outermost layer.

According to the fifth embodiment of the present invention, there isprovided a sanitary ware wherein, in the sanitary ware according to thefirst embodiment of the present invention, the glaze layer as theoutermost layer is a transparent glaze layer and the sanitary warefurther comprises, provided between the sanitary ware body and the glazelayer as the outermost layer, a metal component layer which comprisesthe metal component as a main component, provided on the sanitary warebody side and a colored glaze layer as an intermediate layer provided onthe side of the glaze layer as the outermost layer, the metal componentbeing suppliable from the metal component layer over the whole surfaceof the glaze layer as the outermost layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the distribution of a cleaningmetal component on the surface of the outermost layer of a sanitaryware;

FIG. 2 is a diagram showing the adsorption or addition of a cleaningmetal component onto molecules constituting a stain or soil by asubstitution reaction to render the stain or soluble in water;

FIG. 3 is a diagram illustrating the formation of a hydrated layer onthe surface of a sanitary ware;

FIG. 4 is a diagram showing the layer construction of the sanitary wareaccording to the first embodiment of the present invention, whereinnumeral 1 designates a sanitary ware body and numeral 2 a glaze layer asan outermost layer (the designating of the numerals 1 and 2 in FIG. 4being applied to FIGS. 5 to 8);

FIG. 5 is a diagram showing the layer construction of the sanitary wareaccording to the second embodiment of the present invention, whereinnumeral 3 designates a glaze layer as an intermediate layer (thedesignating of the numeral 3 in FIG. 5 being applied to FIGS. 6 to 8);

FIG. 6 is a diagram showing the layer construction of the sanitary wareaccording to the third embodiment of the present invention, whereinnumeral 4 designates a metal component layer (the designating of thenumeral 4 in FIG. 6 being applied to FIGS. 7 and 8);

FIG. 7 is a diagram showing the layer construction of the sanitary wareaccording to the fourth embodiment of the present invention;

FIG. 8 is a diagram showing the layer construction of the sanitary wareaccording to the fifth embodiment of the present invention;

FIG. 9 is a reflection electron composition image and a mapping image ofthe surface of a glaze layer, in a sanitary ware (Example C1) accordingto the present invention, as measured by an electron probe microanalyzer(JXA 8900RL, manufactured by Japan Electric Optical Laboratory), wherein(a) shows the distribution of potassium, a whiter portion representing ahigher potassium concentration, (b) shows the distribution of sodium, awhiter portion representing a higher sodium concentration, and (c) showsa reflection electron composition image with ZrO₂ being present in awhite portion; and

FIG. 10 is a reflection electron composition image and a mapping imageof the surface of a glaze layer, in a conventional sanitary ware(Comparative Example C1), as measured by an electron probe microanalyzer(JXA 8900RL, manufactured by Japan Electric Optical Laboratory), wherein(a) shows the distribution of potassium, a whiter portion representing ahigher potassium concentration, (b) shows the distribution of sodium, awhiter portion representing a higher sodium concentration, and (c) showsa reflection electron composition image with ZrO₂ being present in awhite portion.

DETAILED DESCRIPTION OF THE INVENTION Definition

The term “sanitary ware” used herein refers to earthenware products usedin or around lavatories and washrooms, and specific examples thereofinclude toilets, urinals, strainers for urinals, flush tanks for toiletsor urinals, washbowls in washstands, and wash hand basins.

The term “earthenware” used herein refers to a ceramic ware, the body ofwhich has been densified to such an extent that the body has slightwater absorption, the ceramic ware having a glazed surface.

Sanitary Ware having Self-cleaning Function

The sanitary ware according to the present invention has a self-cleaningfunction for releasing stains or soils. The “self-cleaning function”refers to such a property that stains or soils on a sanitary ware can besimply removed, for example, by running water without use of anysurfactant and without strongly scrubbing the surface of the sanitaryware by a scrubbing brush or a cleaning brush.

The sanitary ware according to the present invention comprises at leasta sanitary ware body and a glaze layer as an outermost layer of thesanitary ware. According to the present invention, a cleaning metalcomponent is provided so as to be releasable evenly and continuously,over the whole surface of the glaze layer as the outermost layer, insuch an amount large enough to impart a self-cleaning function forreleasing stains or soils to the surface of the glaze layer as theoutermost layer. The cleaning metal component is supplied from the glazelayer as the outermost layer and/or the sanitary ware body to the wholesurface of the glaze layer as the outermost layer.

According to the present invention, the cleaning metal component refersto a monovalent metal component and/or a metal component having ameasure of the electronegativity based on Pouling's rule of not morethan 1. The metal component functions as a detergent (a builder) whichdoes not lose its function upon firing. Specifically, the function isnot lost even after firing of the sanitary ware, that is, after heattreatment at a temperature of 1100 to 1300° C.

Suitable monovalent metal components usable herein include lithium,sodium, potassium, rubidium, cesium, silver, copper, and gold. Suitablemetal components having a measure of the electronegativity based onPouling's rule of not more than 1 usable herein include lithium, sodium,potassium, rubidium, cesium, barium, and strontium. Among the monovalentmetal components, silver and copper are preferred because they furtherhave antimicrobial activity. The content of the cleaning metal componentmay be measured by X-ray photoelectron spectroscopy.

According to the present invention, the glaze layer as the outermostlayer consists essentially of an amorphous component. It is consideredthat, since the amorphous structure is isotropic, the cleaning metalcomponent can be relatively evenly moved in the network structure. As aresult, the cleaning metal component contained in the glaze layer as theoutermost layer and/or the sanitary ware body is movable to andcontinuously releasable to the surface of the outermost layer. Further,according to the present invention, the cleaning metal component isreleased evenly and continuously over the whole surface of the glazelayer as the outermost layer.

In the conventional sanitary ware, since the glaze contains opacifierparticles, such as zircon particles, and pigment particles, theseparticles become exposed to the outermost surface during firing, and theexposed particles inhibit the release of the cleaning metal componentonto the outermost surface. The portions, where the particles areexposed to the outermost surface, do not exhibit the cleaning function.Specifically, since a part of the opacifier particles is exposed on thesurface, the cleaning metal component having the effect of removinggreasy stains and soils is not supplied to these portions. Therefore,even though the cleaning metal component is present on the outermostsurface, greasy stains or soils are deposited with the opacifierparticles serving as the starting point. This makes it impossible tosatisfactorily remove the stains or soils deposited on the surface ofthe sanitary ware by running water alone.

According to the present invention, the inhibiting particles have beenexcluded to realize even and continuous release of the cleaning metalcomponent over the whole surface of the outermost layer of the sanitaryware. FIG. 1 is a schematic diagram showing the distribution of acleaning metal component on the surface of the glaze layer as theoutermost layer of a sanitary ware. As can be seen from FIG. 1, thecleaning metal component is evenly present over the whole surface of theglaze layer as the outermost layer. This imparts significantly improvedgreasy stain and soil deposition preventive properties to the wholesurface of the outermost layer, that is, leads to excellentself-cleaning function.

FIG. 2 illustrates the adsorption or addition of a cleaning metalcomponent onto molecules constituting a stain or soil by a substitutionreaction to render the stain or soil soluble in water. Stains or soilsdeposited on the surface of the sanitary ware include, for example,stool (containing a large amount of oleic acid and bacteria),miroorganisms, such as bacteria and fungi, and water scale in the caseof toilet bowls; water scale, urinary calculi, and bacteria in the caseof urinals; and metal soaps (scum of soaps), fatty acids, fatty esters,proteins, amino acids, and water scale in the case of washbowls. Majordeposited stains and soils are carboxyl-terminated greasy stains orsoils and water scale.

As shown in FIG. 2, upon the deposition of the carboxyl-terminatedgreasy stain or soil on the surface of the sanitary ware, when acleaning metal component (Na⁺ in FIG. 2) is present, the cleaning metalcomponent is preferentially added or adsorbed to the greasy stain orsoil by a substitution reaction. This improves the affinity of thesurface of the sanitary ware for water, and, when the molecular weightof the stain or soil is low, the stain or soil is rendered soluble inwater (saponified). As a result, the affinity of the stain or soil forwater becomes higher than that for the surface of the sanitary ware,permitting the stain or soil to be easily removed by flushing thesanitary ware. Further, in this case, the re-adsorption of the stain orsoil, which has been once left from the surface of the sanitary ware,can be prevented. This advantageous phenomenon is led from the functionof the monovalent metal component and/or the metal component having ameasure of the electronegativity based on Pouling's rule of not morethan 1 as a builder (Yoshiro Abe, “Senzai Tsuron,” KINDAI HENSHUSHA,22-23 (1985)).

The source of supplying the cleaning metal component to the surface ofthe glaze layer as the outermost layer may be any of the glaze layer asthe outermost layer, the sanitary ware body, and the glaze layer as anintermediate layer (when a glaze layer as an intermediate layer isprovided between the glaze layer as the outermost layer and the sanitaryware body). Alternatively, a layer composed mainly of the cleaning metalcomponent may be separately provided as a metal component layer. Byvirtue of this construction, the surface cleaning properties can beexhibited for a long period of time, and the self-cleaning function issemi-permanently ensured.

According to a preferred embodiment of the present invention, thissurface state can be realized by preventing particles, which inhibit therelease of the cleaning metal component onto the outermost surface, forexample particles of opacifiers, such as ZrO₂, and pigments, from beingsubstantially present on the surface of the glaze layer as the outermostlayer. Preferably, this is done, for example, by any of the followingmethods.

(1) Exclusion of inhibiting particles: A transparent glaze is providedwhich contains a cleaning metal component and, at the same time, is freefrom pigment and opacifier particles as inhibiting particles. Thistransparent glaze is coated as an outermost layer onto a sanitary ware,and the coating is fired. Alternatively, a frit glaze, which is freefrom the interfering particles and contains a cleaning metal component,may be provided and then coated as a glaze layer as an outermost layeronto the sanitary ware, followed by firing.

(2) Grinding of inhibiting particles: A frit glaze containing a cleaningmetal component or alternatively a colored glaze containing a cleaningmetal component-containing salt is provided. This glaze is then grounduntil the inhibiting particles are finely divided. This ground coloredglaze is then coated as a glaze layer as an outermost layer onto asanitary ware, followed by firing. The extent of the size reduction ofthe inhibiting particles is preferably such that the average particlediameter as measured with a laser diffraction device is brought to notmore than 6 μm.

According to a preferred embodiment of the present invention, thesurface roughness Ra of the glaze layer as the outermost layer is lessthan 0.07 μm, preferably not more than 0.05 μm, more preferably not morethan 0.03 μm, as measured with a stylus type surface roughness testeraccording to JIS B 0651. This makes it difficult for stains or soils tobe deposited on concave and convex portions of the surface. Thissignificantly improves the self-cleaning function for releasingdeposited stains or soils.

The term “surface roughness Ra” used herein means the value obtained bythe following formula when sampling only the reference length 1 from theroughness curve in the direction of mean line, taking X-axis in thedirection of mean line and Y-axis in the direction of longitudinalmagnification of this sampled part and the roughness curve is expressedby Y=f(x): $R_{a} = {\frac{1}{l}{\int_{0}^{l}{{{f(x)}}{x}}}}$

In the present invention, the surface roughness Ra is in accordance withthe definition and designation specified in JIS B 0601(1994) andmeasured with a stylus type surface roughness tester according to JIS B0651(1996). These JIS, together with English translation thereof, areeasily available from Japanese Standards Association (1-24, Akasaka4-chome, Minato-ku, Tokyo, Japan).

According to a preferred embodiment of the present invention, the glazelayer as the outermost layer consists essentially of an amorphouscomponent (preferably a glass component). It is considered that, sincethis reduces the mobility of the detergent component in the glaze layer,the long-term retention of the self-cleaning function for releasingdeposited stains or soils can be improved.

According to a preferred embodiment of the present invention, the glazelayer as the outermost layer consists essentially of a hydratablematerial. Hydratable materials usable herein include materials whichinclude an SiO₄ network structure having non-crosslinked oxygen throughwhich water molecules can pass (for example, silica and silicate). FIG.3 is a diagram illustrating the formation of a hydrated layer on thesurface of the sanitary ware. As can be seen from FIGS. 2 and 3, thesaponified stain or soil becomes considerably freely movable on thehydratable material as an electrolyte. Therefore, in the sanitary warein its surface which has been inclined in the gravitational direction,the greasy stain or soil is moved in the gravitational direction withoutrelying upon flushing, permitting the stain or soil to be moreautomatically removed.

According to a preferred embodiment of the present invention, the glazelayer as the outermost layer further contains an antimicrobial metal.This can prevent sanitary wares, such as toilets or urinals andwashbowls, from being soiled due to the propagation of bacteria oreumycetes when the sanitary wares are left unused for a long period oftime. According to a more preferred embodiment of the present invention,the antimicrobial metal is silver and/or copper. The content of theantimicrobial metal in the glaze layer as the outermost layer is notless than 0.1% by weight, more preferably not less than 0.5% by weight,in terms of oxide based on the whole metal component in the glaze layeras the outermost layer. This can more effectively prevent sanitarywares, such as toilets or urinals and washbowls, from being soiled dueto the propagation of bacteria or eumycetes when the sanitary wares areleft unused for a long period of time. Silver advantageously has highantimicrobial activity against bacteria, such as Pseudomonas aeruginosa,Eschericia coli, black yeast (black mold), and red yeast (pink slime).On the other hand, copper advantageously has high antimicrobial activityagainst eumycetes, such as mold.

According to a preferred embodiment of the present invention, the zetapotential of the surface of the glaze layer as the outermost layer at apH value of about 7 is negative and has an absolute value of not lessthan 60 mV. This can increase the electrical repulsion of bacteria oreumycetes, present on the surface of the glaze layer as the outermostlayer, against bacteria or eumycetes which are negatively charged inwater generally having a pH value of about 7, thereby more effectivelypreventing the deposition of bacterial or eumycetes. Therefore, theself-cleaning function according to the present invention can be furtherimproved.

The thickness of the glaze layer as the outermost layer is generally0.05 to 1.2 mm, preferably 0.1 to 0.8 mm, more preferably 0.15 to 0.4mm. When the glaze layer as the intermediate layer is provided, thethickness thereof is generally 0.05 to 1.8 mm, preferably 0.1 to 1.2 mm,more preferably 0.2 to 0.7 mm.

Thus, according to the sanitary ware of the present invention, there arevarious embodiments on layer constructions and surface formation methodsfor imparting a self-cleaning function to the surface of the sanitaryware. Five preferred embodiments associated with this will be explained.

Sanitary Ware according to First Embodiment

FIG. 4 shows the layer construction of the sanitary ware according tothe first embodiment of the invention. As can be seen from FIG. 4, thesanitary ware according to the first embodiment of the present inventioncomprises at least a sanitary ware body 1 and a glaze layer 2 as anoutermost layer of the sanitary ware.

In this embodiment, at least one of the sanitary ware body 1 and theglaze layer 2 as the outermost layer is constructed so that a cleaningmetal component is suppliable over the whole surface of the glaze layer2 as the outermost layer and, in this case, is releasable evenly andcontinuously over the whole surface of the glaze layer 2 as theoutermost layer. By virtue of the above mechanism, the surface of thesanitary ware can retain the self-cleaning function for releasingdeposited stains or soils for a long period of time.

According to a preferred embodiment of the present invention, thecleaning metal component is contained in at least the sanitary ware body1. In this preferred embodiment, the cleaning metal component can passthrough the glaze layer 2 as the outermost layer composed mainly of avitreous material and then can function to release stains or soils.Therefore, the sustained release effect can be improved, contributing tothe retention of the self-cleaning function for releasing depositedstains or soils for a longer period of time. Further, in this case, thesanitary ware in its non-glazed surface also can exhibit theself-cleaning function for releasing deposited stains or soils.

According to a more preferred embodiment of the present invention, thecleaning metal component is contained in the glaze layer 2 as theoutermost layer. This can improve also the self-cleaning function forreleasing deposited stains or soils at an early stage in the use of thesanitary ware. The cleaning metal component may be contained in both thesanitary ware body 1 and the glaze layer 2 as the outermost layer.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the glaze layer 2 as theoutermost layer is not less than 7% by weight in terms of oxide based onthe whole metal component in the glaze layer 2 as the outermost layer.This can significantly improve the self-cleaning function for releasingdeposited stains or soils.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the glaze layer 2 as theoutermost layer is less than 20% by weight, more preferably not morethan 15% by weight, in terms of oxide based on the whole metal componentin the glaze layer 2 as the outermost layer. In this case, whilesatisfactorily exhibiting the self-cleaning function for releasingdeposited stains or soil, it is possible to reduce product defectscaused by such a phenomenon that a gas evolved within the sanitary warebody 1 by a chemical reaction or the like of clay at the time of raisingthe temperature stays as bubbles within the glaze without release intothe outside of the sanitary ware body upon shrinkage at the time offiring. Further, cracking due to an increase in a difference incoefficient of thermal expansion, between the glaze layer 2 as theoutermost layer and the sanitary ware body 1, created by an excessiveincrease in the coefficient of thermal expansion of the glaze layer 2 asthe outermost layer can also be prevented.

According to another preferred embodiment of the present invention, anengobe layer may be provided on the surface of the sanitary ware body 1to prevent a gas evolved within the sanitary ware body 1 from enteringthe glaze.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the sanitary ware body 1 isnot less than 5% by weight in terms of oxide based on the whole metalcomponent in the sanitary ware body 1. This can improve the retention ofthe self-cleaning function for releasing deposited stains or soils for along period of time.

The sanitary ware according to the first embodiment of the presentinvention may be produced by any production process without particularlimitation. For example, the following production processes (1) to (4)may be mentioned.

(1) One process for producing the sanitary ware according to the firstembodiment comprises, for example, providing a frit glaze containing notless than 7% by weight, in terms of oxide, of a cleaning metalcomponent, optionally grinding the frit glaze, coating the resultantglaze onto a sanitary ware body, and then firing the coating at atemperature of 1100 to 1300° C.

(2) Another process for producing the sanitary ware according to thefirst embodiment comprises, for example, providing a glaze prepared byadding not less than 7% by weight, in terms of oxide based on the wholemetal component of the glaze, of a salt containing a cleaning metalcomponent to a conventional colored glaze material, grinding the glazeuntil the inhibiting particles are satisfactorily size reduced, coatingthe ground glaze onto a sanitary ware body, and firing the coating at atemperature of 1100 to 1300° C.

(3) Still another process for producing the sanitary ware according tothe first embodiment comprises, for example, providing a glaze composedof a mixture containing a frit, the inhibiting particles and othercomponents, grinding the glaze until the inhibiting particles aresatisfactorily size reduced, coating the ground glaze onto a sanitaryware body, and firing the coating at a temperature of 1100 to 1300° C.

(4) A further process for producing the sanitary ware according to thefirst embodiment comprises, for example, impregnating a cleaning metalcomponent-containing salt into the surface of a sanitary ware body,glazing the sanitary ware body, and then conducting firing at atemperature of 1100 to 1300° C.

Sanitary Ware according to Second Embodiment

FIG. 5 shows the layer construction of the sanitary ware according tothe second embodiment of the present invention. As can be seen from FIG.5, the sanitary ware according to the second embodiment of the presentinvention comprises a sanitary ware body 1, a colored glaze layer 3 asan intermediate layer provided on the surface of the sanitary ware body1, and a transparent glaze layer 2 as an outermost layer of the sanitaryware.

In this embodiment, at least one of the sanitary ware body 1, the glazelayer 2 as the outermost layer, and the glaze layer 3 as theintermediate layer is constructed so that a cleaning metal component issuppliable over the whole surface of the glaze layer 2 as the outermostlayer and, in this case, is releasable evenly and continuously over thewhole surface of the glaze layer 2 as the outermost layer. By virtue ofthe above mechanism, the surface of the sanitary ware can retain theself-cleaning function for releasing deposited stains or soils for along period of time.

In particular, according to the second embodiment, the glaze layer 2 asthe outermost layer of the sanitary ware is a transparent glaze layerfree from the inhibiting particles, such as pigment and opacifierparticles. Therefore, the cleaning metal component can be releasedevenly and continuously over the whole surface of the glaze layer 2 asthe outermost layer, the sustained release effect of the cleaning metalcomponent can be improved, and the self-cleaning function according tothe present invention can be retained for a long period of time.Further, the components of the glaze layer 2 as the outermost layer canbe selected independently of the compatibility with the sanitary warebody in terms of the coefficient of thermal expansion or the like.Therefore, a larger amount of the cleaning metal component can beincorporated into the glaze layer 2 as the outermost layer, and, thus,the self-cleaning function at an early stage in the use of the sanitaryware can also be improved.

According to a preferred embodiment of the present invention, thecleaning metal component is contained in at least the glaze layer 2 asthe outermost layer. The components of the glaze layer 2 as theoutermost layer can be selected independently of the compatibility withthe sanitary ware body 1 in terms of the coefficient of thermalexpansion. Therefore, a larger amount of the cleaning metal componentcan be incorporated into the glaze layer 2 as the outermost layer, and,thus, the self-cleaning function for releasing deposited stains or soilsat an early stage in the use of the sanitary ware can also be improved.

According to a preferred embodiment of the present invention, thecleaning metal component is contained in at least one of the sanitaryware body 1 and the glaze layer 3 as the intermediate layer. In thispreferred embodiment, the cleaning metal component can pass through theglaze layer 2 as the outermost layer composed mainly of a vitreousmaterial and then can function to release stains or soils. Therefore,the sustained release effect can be improved, contributing to theretention of the self-cleaning function for releasing deposited stainsor soils for a longer period of time.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the glaze layer 2 as theoutermost layer is not less than 7% by weight in terms of oxide based onthe whole metal component in the glaze layer 2 as the outermost layer.This can significantly improve the self-cleaning function for releasingdeposited stains or soils.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the glaze layer 2 as theoutermost layer is less than 30% by weight, more preferably not morethan 20% by weight, still more preferably not more than 15% by weight,in terms of oxide based on the whole metal component in the glaze layer2 as the outermost layer. In this case, while satisfactorily exhibitingthe self-cleaning function for releasing-deposited stains or soil, it ispossible to reduce product defects caused by such a phenomenon that agas evolved within the sanitary ware body 1 in a chemical reaction orthe like of clay at the time of raising the temperature stays as bubbleswithin the glaze without release into the outside of the sanitary warebody upon shrinkage at the time of firing.

According to a preferred embodiment of the present invention, thecontent of the cleaning metal component in the sanitary ware body 1 isnot less than 5% by weight in terms of oxide based on the whole metalcomponent in the sanitary ware body 1. This can improve the retention ofthe self-cleaning function for releasing deposited stains or soils for along period of time.

The sanitary ware according to the second embodiment may be produced byany production process without particular limitation. For example, thesanitary ware according to the second embodiment may be produced bycoating a conventional colored glaze onto a sanitary ware body, furthercoating a (frit) glaze containing a cleaning metal component in anamount of not less than 7% by weight in terms of oxide and free from apigment and an opacifier onto the colored glaze coating and thenconducting firing at a temperature of 1100 to 1300° C.

Sanitary Ware according to Third Embodiment

FIG. 6 shows the layer construction of the sanitary ware according tothe third embodiment of the present invention. As can be seen from FIG.6, the sanitary ware according to the third embodiment of the presentinvention comprises a sanitary ware body 1, a metal component layer 4,composed mainly of a cleaning metal component, provided on the surfaceof the sanitary ware body, and a glaze layer 2 as an outermost layer ofthe sanitary ware provided on the surface of the metal component layer.

In this embodiment, the cleaning metal component is suppliable, mainlyby the metal component layer 4, to the whole surface of the glaze layer2 as the outermost layer and, in this case, is releasable evenly andcontinuously over the whole surface of the glaze layer 2 as theoutermost layer. By virtue of the above mechanism, the surface of thesanitary ware can retain the self-cleaning function for releasingdeposited stains or soils for a long period of time.

In particular, the sanitary ware according to the third embodiment hasthe sanitary ware body 1 and the glaze layer 2 as the outermost layer asused in the sanitary ware according to the first embodiment of thepresent invention. Further, a metal component layer 4 as a source forthe cleaning metal component is provided between the sanitary ware body1 and the glaze layer 2 as the outermost layer. This can furtherincrease the amount of the cleaning metal component stored in thesanitary ware, and, at the same time, can improve the sustained releaseeffect of the cleaning metal component. Therefore, the surface of thesanitary ware can exhibit the self-cleaning function for releasingdeposited stains or soils for a longer period of time. The cleaningmetal component may be contained in both the sanitary ware body 1 and/orthe glaze layer 2 as the outermost layer.

The metal component layer 4 is a layer composed mainly of a cleaningmetal component. Preferably, the cleaning metal component consistsessentially of a compound composed mainly of the cleaning metalcomponent. Preferred cleaning metal component-containing compoundsusable herein include sodium carbonate, potassium carbonate, lithiumcarbonate, cesium carbonate, rubidium carbonate, barium carbonate,strontium carbonate, silver carbonate, copper(I) carbonate, sodiumsilicate, potassium silicate, lithium silicate, cesium silicate,rubidium silicate, barium silicate, strontium silicate, silver silicate,copper(I) silicate, sodium chloride, potassium chloride, lithiumchloride, cesium chloride, rubidium chloride, barium chloride, strontiumchloride, silver chloride, copper(I) chloride, sodium acetate, potassiumacetate, lithium acetate, cesium acetate, rubidium acetate, bariumacetate, strontium acetate, silver acetate, copper(I) acetate, sodiumsulfate, potassium sulfate, lithium sulfate, cesium sulfate, rubidiumsulfate, barium sulfate, strontium sulfate, silver sulfate, copper(I)sulfate, sodium nitrate, potassium nitrate, lithium nitrate, cesiumnitrate, rubidium nitrate, barium nitrate, strontium nitrate, silvernitrate, copper(I) nitrate, sodium lactate, potassium lactate, lithiumlactate, cesium lactate, barium lactate, rubidium lactate, strontiumlactate, silver lactate, copper(I) lactate, sodium borate, potassiumborate, lithium borate, cesium borate, rubidium borate, barium borate,strontium borate, sodium propionate, potassium propionate, lithiumpropionate, cesium propionate, rubidium propionate, barium propionate,strontium propionate, silver propionate, copper(I) propionate, sodiumbutyrate, potassium butyrate, lithium butyrate, cesium butyrate,rubidium butyrate, barium butyrate, strontium butyrate, silver butyrate,copper(I) butyrate, sodium formate, potassium formate, lithium formate,cesium formate, rubidium formate, barium formate, strontium formate,silver formate, copper(I) formate, gold(I) chloride, liquid bright gold,gold powder, silver powder, water glass, H(AuCl₄)·4H₂O, andNa(AuCl₄)·2H₂O.

The sanitary ware according to the third embodiment of the presentinvention may be produced by any production process without particularlimitation. For example, the following production processes (1) and (2)may be mentioned.

(1) One process for producing the sanitary ware according to the thirdembodiment comprises first coating a material with a cleaning metalcomponent being incorporated therein by firing, such as water glass,onto a sanitary ware body to form a metal component layer, providing acolored glaze, grinding the colored glaze until interfering particlesare satisfactorily size reduced, coating the ground colored glaze ontothe metal component layer, and then conducting firing at a temperatureof 1100 to 1300° C.

(2) Another process for producing the sanitary ware according to thethird embodiment comprises first coating a cleaning metalcomponent-containing material, such as water glass, onto a sanitary warebody to form a metal component layer, providing a frit glaze of acleaning metal component, optionally grinding the frit glaze, coatingthe frit glaze onto the metal component layer, and then conductingfiring at a temperature of 1100 to 1300° C.

Sanitary Ware according to Fourth Embodiment

FIG. 7 shows the layer construction of the sanitary ware according tothe fourth embodiment of the present invention. As can be seen from FIG.7, the sanitary ware according to the fourth embodiment of the presentinvention comprises at least a sanitary ware body 1, a colored glazelayer 3 as an intermediate layer provided on the surface of the sanitaryware body 1, a metal component layer 4, composed mainly of a cleaningmetal component, provided on the surface of the glaze layer as theintermediate layer, and a transparent glaze layer 2 as an outermostlayer of the sanitary ware provided on the surface of the metalcomponent layer.

In the fourth embodiment, the cleaning metal component is suppliable,mainly by the metal component layer 4, to the whole surface of the glazelayer 2 as the outermost layer and, in this case, is releasable evenlyand continuously over the whole surface of the glaze layer 2 as theoutermost layer. By virtue of the above mechanism, the surface of thesanitary ware can retain the self-cleaning function for releasingdeposited stains or soils for a long period of time.

In particular, the sanitary ware according to the fourth embodiment hasthe sanitary ware body 1, the glaze layer 3 as the intermediate layer,the glaze layer 2 as the outermost layer as used in the sanitary wareaccording to the second embodiment of the present invention. The metalcomponent layer 4 as used in the third embodiment is provided, as asource for the cleaning metal component, between the glaze layer 3 asthe intermediate layer and the glaze layer 2 as the outermost layer. Theglaze layer 2 as the outermost layer is a transparent glaze layer freefrom interfering particles, such as pigment and opacifier particles,and, in addition, the metal component layer 4 can function as a sourcefor the cleaning metal component. Therefore, the cleaning metalcomponent can be easily released evenly and continuously over the wholesurface of the glaze layer 2 as the outermost layer, and theself-cleaning function according to the present invention can besatisfactorily exhibited and, at the same time, can be retained for alonger period of time.

The sanitary ware according to the fourth embodiment of the presentinvention may be produced by any production process without particularlimitation. For example, the sanitary ware may be produced by aproduction process which comprises coating a conventional colored glazeon a sanitary ware body, coating a cleaning metal component-containingmaterial, such as water glass, onto the glaze layer to form a metalcomponent layer, and coating a glaze containing neither a pigment nor anopacifier, and then conducting firing at a temperature of 1100 to 1300°C.

Sanitary Ware according to Fifth Embodiment

FIG. 8 shows the layer construction of the sanitary ware according tothe fifth embodiment of the present invention. As can be seen from FIG.8, the sanitary ware according to the fifth embodiment of the presentinvention comprises a sanitary ware body 1, a metal component layer 4,composed mainly of a cleaning metal component, provided on the surfaceof the sanitary ware body, a colored glaze layer 3 as an intermediatelayer provided on the surface of the metal component layer, and atransparent glaze layer 2 as an outermost layer of the sanitary wareprovided on the surface of the glaze layer as the intermediate layer.

In the fifth embodiment of the present invention, the cleaning metalcomponent is suppliable, mainly by the metal component layer 4, to thewhole surface of the glaze layer 2 as the outermost layer and, in thiscase, is releasable evenly and continuously over the whole surface ofthe glaze layer 2 as the outermost layer. By virtue of the abovemechanism, the surface of the sanitary ware can retain the self-cleaningfunction for releasing deposited stains or soils for a long period oftime.

In particular, the sanitary ware according to the fifth embodiment ofthe present invention has the sanitary ware body 1, the glaze layer 3 asthe intermediate layer, the glaze layer 2 as the outermost layer as usedin the sanitary ware according to the second embodiment of the presentinvention. The metal component layer 4 as used in the third embodimentis provided, as a source for the cleaning metal component, between thesanitary ware body 1 and the glaze layer 3 as the intermediate layer.The glaze layer 2 as the outermost layer is a transparent glaze layerfree from interfering particles, such as pigment and opacifierparticles, and, in addition, the metal component layer 4 can function asa source for the cleaning metal component. Therefore, the cleaning metalcomponent can be released evenly and continuously over the whole surfaceof the glaze layer 2 as the outermost layer, and the self-cleaningfunction according to the present invention can be satisfactorilyexhibited and, at the same time, can be retained for a longer period oftime.

The sanitary ware according to the fifth embodiment of the presentinvention may be produced by any production process without particularlimitation. For example, the sanitary ware may be produced by aproduction process which comprises coating a cleaning metalcomponent-containing material, such as water glass, onto a sanitary warebody, coating a conventional colored glaze, coating a glaze containingneither a pigment nor an opacifier, onto the glaze layer, and thenconducting firing at a temperature of 1100 to 1300° C.

Applications

The sanitary ware according to the present invention refers toearthenware products used in or around lavatories and washrooms, and canbe applied to a wide variety of applications, such as toilets, urinals,strainers for urinals, flush tanks for toilets or urinals, washbowls inwashstands, and wash hand basins.

According to a preferred embodiment of the present invention, thesanitary ware is a toilet or a urinal.

Main components of feces discharged from human beings are oleic acid andbacteria. Both the oleic acid and the bacteria are carboxyl terminalgroup-containing substances. Therefore, when the sanitary ware accordingto the present invention is applied to a toilet, feces are less likelyto be deposited onto the bowl surface of the toilet because they areremoved upon flushing of the bowl.

Upon the deposition of water scale onto the toilet, the scale depositedsurface is changed from a hydrophilic state to a water-repellent state.As a result, upon flushing, water does not flow on the water-repellentsurface, and this causes staining or soiling at an increasingly rapidpace. The application of the sanitary ware according to the presentinvention to the toilet can solve this problem and enables water to runover the whole surface of the toilet bowl. Therefore, it is possible toprovide toilets wherein stains or soils are less likely to be depositedonto the toilet bowl.

When water scale accumulates on a toilet or a urinal to a certainthickness, the toilet or urinal is cracked. Microorganisms, such asmold, propagate in the cracked portion. It is considered that, as soonas the number of microorganisms exceeds a predetermined value, thesemicroorganisms are seen as black soils. The application of the sanitaryware according to the present invention to the toilet or urinal cansolve this problem and can prevent the formation of the water scalefilm. Therefore, it is possible to provide toilets or urinals whereinblack soils are less likely to be deposited.

Upon the deposition of urinary calculi onto a toilet or a urinal, thedeposited portion serves as a hotbed of the propagation of eumycetes orbacteria. When the number of eumycetes or bacteria exceeds a certainvalue, these eumycetes or bacteria are seen as yellow, pink, or brownsoils. The application of the sanitary ware according to the presentinvention to the toilet or urinal can prevent urinary calculi, whichserve as a hotbed of the propagation of eumycetes or bacteria, frombeing deposited on the toilet or urinal. Therefore, it is possible toprovide toilets or urinals which are less likely to be soiled.

According to another preferred embodiment of the present invention, thesanitary ware is a washbowl.

Major components of soils or stains in the washbowl are lipids (fattyesters) derived form human beings and scum of soaps (calcium salts offatty acids), both of which are carboxyl terminal group-containingsubstances. Therefore, when the sanitary ware according to the presentinvention is applied to the washbowl, these soils or stains are lesslikely to be deposited onto the washbowl because they are removed byflushing from the bowl surface.

EXAMPLES

The present invention will be described in more detail with reference tothe following examples, though it is not limited to these examples only.

Composition of Glaze

A material A for a glaze used in the following examples and comparativeexamples has a composition shown in Table 1.

TABLE 1 Material for glaze wt % SiO₂ 55-80 Al₂O₃  5-13 Fe₂O₃ 0.1-0.4 MgO0.8-3.0 CaO  8-17 ZnO 3-8 K₂O 1-4 Na₂O 0.5-2.5 ZrO₂ 0.1-15  Pigment 1-20

Testing Methods

In the following examples and comparative examples, evaluation testswere carried out by the following methods.

Test 1: Surface Roughness of Glaze Layer as the Outermost Layer

The surface roughness Ra of the glaze layer was measured with a stylustype surface roughness tester (JIS B 0651).

Test 2: Zeta Potential of the Surface of the Glaze Layer

The zeta potential of the surface of the glaze layer was measured with alaser zeta electrometer (ELS-6000, manufactured by Otsuka Denshi K.K.).Specifically, the electroosmotic fluid flow was measured using anaqueous NaCl solution (pH 7.0, concentration 10 mM) as an electrolyteand a polystyrene latex as monitor particles for light scattering, andthen analyzed by the Mori-Okamoto's equation.

Test 3: Antimicrobial Activity

The antimicrobial activity was evaluated by measuring the bactericidalactivity against E. coli (Eschericia coli, IFO 3972).

A bacterial suspension (0.2 ml) (number of bacteria: 1×10⁵ to 5×10⁵) wasdropped on the surface of the glaze layer in a sample which had beenpreviously sterilized with 70 vol % ethanol and then dried. The glazelayer was then covered with a polyethylene film having a size of 45mm×45 mm to intimately contact the bacterial suspension with the sample.The specimen thus obtained was then allowed to stand for 24 hr in anatmosphere having a temperature of 37±1° C. and a relative humidity ofnot less than 90%. Thereafter, the film was separated, and imprintingwas carried out in an NA medium, followed by cultivation under anenvironment having a temperature of 35±1° C. for 16 to 20 hr. The vialcell count (hereinafter referred to as “vial cell count for the testsample”) was then measured.

Separately, for a blank sample having no significant antimicrobialactivity (control sample), in the same manner as described above, aspecimen was prepared, and the vial cell count (hereinafter referred toas “vial cell count for the control sample”) was then measured.

The sterilization and the growth inhibition were calculated based on thevial cell count for the test sample and the vial cell count for thecontrol sample by the following equations to evaluate the antimicrobialactivity.

Sterilization (%)=100×(“vial cell count for control sample”−“vial cellcount for test sample”)/“vial cell count for control sample”)

Growth inhibition=log(“vial cell count for control sample”/“vial cellcount for control sample”)

Test 4: Resistance to Dummy Stain in Water

A dummy stain consisting of 200 parts by weight of oleic acid, 1 part byweight of an engine oil, and 1 part by weight of oil black was prepared.Oleic acid is a main component of feces. The engine oil and the oilblack were used as additives for rendering the oil easily visible. Next,about 270 cc of distilled water was placed in a 300 cc beaker, and about30 cc of the dummy stain was then added thereto. A plate specimen wasimmersed in the beaker, and the time, elapsed until the oil staindeposited on the surface of the glaze layer was separated in water, wasmeasured.

Test 5: Resistance to Dummy Stain in Air

A dummy stain (0.3 cc) having the same composition as used in test 4 wasdropped on the center of a horizontally placed plate specimen. The platespecimen was then stood vertically. Five min after the vertical standingof the sample, the sample was visually inspected for the residual dummystain on the glaze surface.

Test 6: Visual Inspection of Glaze Layer in its Surface

The appearance of the glaze layer in its surface was visually evaluated.

Test 7: Analysis of Glaze Layer in its Surface

The surface of the glaze layer was analyzed by an electron probemicroanalyzer (EPMA: JXA 8900 RL, manufactured by Japan Electric OpticalLaboratory).

Example A1

The material A for a glaze (2 kg), 1 kg of water, and 4 kg of balls wereplaced in a ceramic pot having a volume of 6 liters, and the mixture wasthen ball milled for about 18 hr to obtain a glaze slurry as a glaze A.The particle diameter of the glaze A thus obtained was measured with alaser diffraction particle size distribution analyzer. As a result, itwas found that 65% of the particles were accounted for by particleshaving a diameter of not more than 10 μm and the 50% average particlediameter (D50) was 5.8 μm.

Separately, a material for a glaze was provided which had the samecomposition as the material A for a glaze, except that ZrO₂ as theopacifier and the pigment were removed from the composition of thematerial A for a glaze. This material for a glaze was melted at 1300 to1400° C. in an electric furnace, and the melt was then quenched in waterto obtain a glass frit. The glass frit was then stamp milled to obtain apowder. The powder thus obtained (600 g), 3.0 g (0.5% by weight based onthe glaze) of a silver powder, 400 g of water, and 1 kg of alumina ballswere placed in a ceramic pot having a volume of 2 liters, and themixture was then ball milled for about 24 hr. Thus, a glaze slurry as aglaze B was obtained. The particle diameter of the glaze B was measuredwith a laser diffraction particle size distribution analyzer. As aresult, it was found that 68% of the particles were accounted for byparticles having a diameter of not more than 10 μm and the 50% averageparticle diameter (D50) was 6.0 μm.

Next, a plate specimen having a size of 70×150 mm was prepared using aslurry for a sanitary ware body prepared using silica sand, feldspar,clay and the like as raw materials. The glaze A was spray coated ontothe plate specimen to form a lower glaze layer, and the glaze B was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1 to 3 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.02 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −68.3 mV.

Test 3: The sterilization was 99.994%, and the growth inhibition was4.2. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Example A2

A material for a glaze was provided which had the same composition asthe material A for a glaze, except that the ZrO₂ as the opacifier andthe pigment were removed from the composition of the material A for aglaze. This material for a glaze was melted at 1300 to 1400° C. in anelectric furnace, and the melt was then quenched in water to obtain aglass frit. The glass frit was then stamp milled to obtain a powder. Thepowder thus obtained (600 g), 6.0 g (1.0% by weight based on the glaze)of a copper oxide powder, 400 g of water, and 1 kg of alumina balls wereplaced in a ceramic pot having a volume of 2 liters, and the mixture wasthen ball milled for about 24 hr. Thus, a glaze slurry as a glaze C wasobtained. The particle diameter of the glaze C thus obtained wasmeasured with a laser diffraction particle size distribution analyzer.As a result, it was found that 68% of the particles were accounted forby particles having a diameter of not more than 10 μm and the 50%average particle diameter (D50) was 6.0 μm.

Next, the glaze A was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze C was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1 to 3 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −60.2 mV.

Test 3: The sterilization was 99.0%, and the growth inhibition was 2.0.Based on these results, the sample was evaluated as having significantantimicrobial activity.

Example A3

The frit glaze slurry (free from the opacifier and the pigment, D50=6.0μm) (80 parts by weight) prepared in Example A1 was mixed with 20 partsby weight of a glaze slurry (D50=5.9 μm), free from the opacifier andthe pigment, before fritting. A silver powder was added in an amount of0.5% by weight based on the solid content of the glaze to the mixedslurry, followed by stirring and mixing by means of a plunger. Thus, aglaze slurry as a glaze D was obtained. The particle diameter of theglaze D was measured with a laser diffraction particle size distributionanalyzer. As a result, it was found that 57% of the particles wereaccounted for by particles having a diameter of not more than 10 μm andthe 50% average particle diameter (D50) was 6.0 μm.

Next, the glaze A was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze D was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample, tests 1 to 3 described above were carried out. Theresults were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.05 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −61.3 mV.

Test 3: The sterilization was 99.991%, and the growth inhibition was4.0. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Example A4

The material A for a glaze (600 g), 3.0 g (0.5% by weight based on theglaze) of a silver powder, 400 g of water, and 1 kg of alumina ballswere placed in a ceramic pot having a volume of 2 liters, and themixture was then ball milled for about 65 hr. Thus, a glaze slurry as aglaze E was obtained. The particle diameter of the glaze E was measuredwith a laser diffraction particle size distribution analyzer. As aresult, it was found that 98% of the particles were accounted for byparticles having a diameter of not more than 10 μm and the 50% averageparticle diameter (D50) was 1.2 μm.

Next, the glaze E was spray coated onto the same plate specimen as usedin Example A1, followed by firing at 1100 to 1200° C. to obtain asample.

For the sample, tests 1 to 3 described above were carried out. Theresults were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.02 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −62.4 mV.

Test 3: The sterilization was 99.990%, and the growth inhibition was4.0. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Comparative Example A1

The glaze A was spray coated onto the same plate specimen as used inExample A1, followed by firing at 1100 to 1200° C. to obtain a sample.

For the sample, tests 1 to 3 described above were carried out. Theresults were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.10 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −57.2 mV.

Test 3: The sterilization was 25%, and the growth inhibition was 0.12.Based on these results, the sample was evaluated as having nosignificant antimicrobial activity.

The results of evaluation in Examples A1 to A4 of the present inventionand Comparative Example A1 are summarized in Table 2.

TABLE 2 Surface Zeta roughness, potential Antimicrobial test Ra (pH:7)Growth inhibition Example A1 0.02 μm −68.3 mV 4.2 Example A2 0.03 μm−60.2 mV 2.0 Example A3 0.05 μm −61.3 mV 4.0 Example A4 0.02 μm −62.4 mV4.0 Comparative 0.07 μm −57.2 mV 0.12 Example A1

Example B1

A material for a glaze was provided which had the same composition asthe material A for a glaze shown in Table 1, except that the ZrO₂ as theopacifier and the pigment were removed from the composition of thematerial A for a glaze and the content of the Na₂O component wasincreased so that, for the monovalent metal component, the total weightof K₂O and Na₂O was 10% by weight based on the total weight of the glasscomponent. This material for a glaze was melted at 1300 to 1400° C. inan electric furnace, and the melt was then quenched in water to obtain aglass frit. The glass frit was then stamp milled to obtain a powder. Thepowder thus obtained. (600 g), 3.0 g (0.5% by weight based on the glaze)of a silver powder, 400 g of water, and 1 kg of alumina balls wereplaced in a ceramic pot having a volume of 2 liters, and the mixture wasthen ball milled for about 24 hr. Thus, a glaze slurry as a glaze F wasobtained. The particle diameter of the glaze F thus obtained wasmeasured with a laser diffraction particle size distribution analyzer.As a result, it was found that 68% of the particles were accounted forby particles having a diameter of not more than 10 μm and the 50%average particle diameter (D50) was 6.0 μm.

Next, the glaze A was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze F was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1 to 5 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.02 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −68.3 mV.

Test 3: The sterilization was 99.994%, and the growth inhibition was4.2. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Test 4: Thirty five sec after the submergence, the oil film wassubstantially completely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Example B2

A material for a glaze was provided which had the same composition asthe material A for a glaze, except that the ZrO₂ as the opacifier andthe pigment were removed from the composition of the material A for aglaze and, in addition, a sodium carbonate powder and a silver powderwere added so that, for the monovalent metal component, the total weightof K₂O and Na₂O was 10% by weight based on the total weight of the glasscomponent and the weight of silver was 0.5% by weight. The mixture wasthen stirred for about 3 hr. Thus, a glaze slurry as a glaze G wasobtained. The particle diameter of the glaze G was measured with a laserdiffraction particle size distribution analyzer. As a result, it wasfound that 68% of the particles were accounted for by particles having adiameter of not more than 10 μm and the 50% average particle diameter(D50) was 6.0 μm.

Next, the glaze A was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze G was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1 to 5 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −66.5 mV.

Test 3: The sterilization was 99.991%, and the growth inhibition was4.0. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Test 4: Thirty sec after the submergence, the oil film was substantiallycompletely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Example B3

A material for a glaze was provided which had the same composition asthe material A for a glaze shown in Table 1, except that the ZrO₂ as theopacifier and the pigment were removed from the composition of thematerial A for a glaze and the content of the Na₂O component wasincreased so that, for the monovalent metal component, the total weightof K₂O and Na₂O was 20% by weight based on the total weight of the glasscomponent. The material for a glaze (2 kg), 10 g (0.5% by weight basedon the glaze) of a silver powder, 1 kg of water, and 4 kg of balls wereplaced in a ceramic pot having a volume of 6 liters, and the mixture wasthen ball milled for about 20 hr. Thus, a glaze slurry as a glaze H wasobtained. The particle diameter of the glaze H was measured with a laserdiffraction particle size distribution analyzer. As a result, it wasfound that 63% of the particles were accounted for by particles having adiameter of not more than 10 μm and the 50% average particle diameter(D50) was 6.5 μm.

A material for a glaze was provided which had the same composition asthe material A for a glaze shown in Table 1, except that the ZrO₂ as theopacifier and the pigment were removed from the composition of thematerial A for a glaze (for the monovalent metal component, the totalweight of K₂O and Na₂O=3.5% by weight based on the total weight of theglass component). This material for a glaze was melted at 1300 to 1400°C. in an electric furnace, and the melt was then quenched in water toobtain a glass frit. The glass frit was then stamp milled to obtain apowder. The powder thus obtained (600 g), 400 g of water, and 1 kg ofalumina balls were placed in a ceramic pot having a volume of 2 liters,and the mixture was then ball milled for about 18 hr. Thus, a glazeslurry as a glaze I was obtained. The particle diameter of the glaze Iwas measured with a laser diffraction particle size distributionanalyzer. As a result, it was found that 68% of the particles wereaccounted for by particles having a diameter of not more than 10 μm andthe 50% average particle diameter (D50) was 6.0 μm.

Next, the glaze A was spray coated onto the same plate specimen as usedin Example A1 to form a first glaze layer. The glaze I was then spraycoated on the first glaze layer to form a second glaze layer.Thereafter, the glaze H was spray coated on the second glaze layer toform a third glaze layer, followed by firing at 1100 to 1200° C. toobtain a sample.

For the sample thus obtained, tests 1 to 5 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −72.0 mV.

Test 3: The sterilization was 99.9991%, and the growth inhibition was5.0. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Test 4: Forty five sec after the submergence, the oil film wassubstantially completely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Example B4

The glaze A as used in Example A1 was spray coated onto the same platespecimen as used in Example A1 to form a lower glaze layer. A glazeslurry prepared by adding 0.5% by weight of silver to the glaze Iprepared in Example B3 and then stirring the mixture for about 3 hr wasthen spray coated on the lower glaze layer to form an upper glaze layer.Further, 1.0 g of an aqueous sodium carbonate solution (concentration10%) was sprayed thereon, followed by firing at 1100 to 1200° C. toobtain a sample.

For the sample thus obtained, tests 1 to 5 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −68.8 mV.

Test 3: The sterilization was 99.994%, and the growth inhibition was4.2. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Test 4: Sixty sec after the submergence, the oil film was substantiallycompletely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Example B5

An aqueous sodium carbonate solution (concentration 20%) (1.0 g) wassprayed on the same plate specimen as used in Example A1. Thereafter,the glaze A as used in Comparative Example A1 was spray coated onto theplate specimen to form a lower glaze layer. A glaze slurry prepared byadding 0.5% by weight of silver to the glaze I prepared in Example B3and then stirring the mixture for about 3 hr was then spray coated onthe lower glaze layer to form an upper glace layer, followed by firingat 1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1 to 5 described above were carriedout. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −67.5 mV.

Test 3: The sterilization was 99.990%, and the growth inhibition was4.0. Based on these results, the sample was evaluated as havingsignificant antimicrobial activity.

Test 4: Forty five sec after-the submergence, the oil film wassubstantially completely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

The results of evaluation in Examples B1 to B5 of the present inventionare summarized in Table 3.

TABLE 3 Surface roughness Stain resistance test Zeta potentialAntimicrobial test Ra In water In air (pH: 7) Growth inhibition Example0.02 μm 35 sec A −68.3 mV 4.2 B1 Example 0.03 μm 30 sec A −66.5 mV 4.0B2 Example 0.03 μm 35 sec A −72.0 mV 5.0 B3 Example 0.03 μm 60 sec A−68.8 mV 4.2 B4 Example 0.03 μm 45 sec A −67.5 mV 4.0 B5 Reference) Zetapotential of E. coli at pH 7: −41 mV Note) “Stain resistance test (inair)” A: The oil film was substantially completely run down. B: A partof the oil film stayed on the plate specimen. C: The oil film in itslarge part stayed on the plate specimen.

Example C1

The material A for a glaze (for the monovalent metal component, thetotal weight of K₂O and Na₂O=3.5% by weight based on the total weight ofthe glass component; the content of Li₂O component=0% by weight) (2 kg),1 kg of water, and 4 kg of balls were placed in a ceramic pot having avolume of 6 liters, and the mixture was then ball milled for about 18hr. Thus, a glaze slurry as a glaze J was obtained. The particlediameter of the glaze J was measured with a laser diffraction particlesize distribution analyzer. As a result, it was found that 65% of theparticles were accounted for by particles having a diameter of not morethan 10 μm and the 50% average particle diameter (D50) was 5.8 μm.

The material for a glaze was provided which had the same composition asthe material A for a glaze, except that the ZrO₂ as the opacifier andthe pigment were removed from the composition of the material A for aglaze and the content of the Na₂O component was increased (for themonovalent metal component, the total weight of K₂O and Na₂O=10% byweight based on the total weight of the glass component; the content ofLi₂O component=0% by weight). This material for a glaze was melted at1300 to 1400° C. in an electric furnace, and the melt was then quenchedin water to obtain a glass frit. The glass frit was then stamp milled toobtain a powder. The powder thus obtained (600 g), 400 g of water, and 1kg of alumina balls were placed in a ceramic pot having a volume of 2liters, and the mixture was then ball milled for about 24 hr. Thus, aglaze slurry as a glaze K was obtained. The particle diameter of theglaze K thus obtained was measured with a laser diffraction particlesize distribution analyzer. As a result, it was found that 68% of theparticles were accounted for by particles having a diameter of not morethan 10 μm and the 50% average particle diameter (D50) was 6.0 μm.

Next, the glaze J was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze K was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1, 2 and 4 to 7 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.04 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −68.3 mV.

Test 4: Thirty five sec after the submergence, the oil film wassubstantially completely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Test 7: A reflection electron composition image and a mapping image onthe surface of the glaze layer are shown in FIG. 9. As can be seen fromFIG. 9, ZrO₂ as the opacifier and silica particles remaining undissolvedwere absent on the surface of the glaze layer, and builder components(for example, sodium and potassium) were observed over the whole surfaceof the glaze layer, indicating that builder components (for example,sodium and potassium) could be released over the whole surface of theglaze layer.

Example C2

A material for a glaze was prepared which had the same composition asthe material A for a glaze, except that the ZrO₂ as the opacifier andthe pigment were removed from the composition of the material A for aglaze (for the monovalent metal component, the total weight of K₂O andNa₂O=3.6% by weight based on the total weight of the glass component;the content of Li₂O component=0% by weight). This material for a glazewas melted at 1300 to 1400° C. in an electric furnace, and the melt wasthen quenched in water to obtain a glass frit. The glass frit was thenstamp milled to obtain a powder. The powder thus obtained (600 g), 400 gof water, and 1 kg of alumina balls were placed in a ceramic pot havinga volume of 2 liters, and the mixture was then ball milled for about 18hr. A sodium carbonate powder was added to the glaze slurry thusobtained (for the monovalent metal component, the total weight of K₂Oand Na₂O=10% by weight based on the total weight of the glass component;the content of Li₂O component=0% by weight), and the mixture was stirredfor about one hr. Thus, a glaze slurry as a glaze L was obtained. Theparticle diameter of the glaze L was measured with a laser diffractionparticle size distribution analyzer. As a result, it was found that 68%of the particles were accounted for by particles having a diameter ofnot more than 10 μm and the 50% average particle diameter (D50) was 6.0μm.

Next, the glaze J was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze L was thenspray coated thereon to form an upper glaze layer, followed by firing at1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1, 2 and 4 to 6 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.03 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −66.5 mV.

Test 4: Thirty sec after the submergence, the oil film was substantiallycompletely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Example C3

A material for a glaze was provided which had the same composition asthe material A for a glaze, except that the ZrO₂ as the opacifier andthe pigment were removed from the composition of the material A for aglaze and the content of the Na₂O component was increased (for themonovalent metal component, the total weight of K₂O and Na₂O was 20% byweight based on the total weight of the glass component; the content ofthe Li₂O component=0% by weight). The material for a glaze (2 kg), 1 kgof water, and 4 kg of balls were placed in a ceramic pot having a volumeof 6 liters, and the mixture was then ball milled for about 20 hr. Thus,a glaze slurry as a glaze M was obtained. The particle diameter of theglaze M was measured with a laser diffraction particle size distributionanalyzer. As a result, it was found that 63% of the particles wereaccounted for by particles having a diameter of not more than 10 μm andthe 50% average particle diameter (D50) was 6.5 μm.

Separately, a material for a glaze was provided which had the samecomposition as the material A for a glaze, except that the ZrO₂ as theopacifier and the pigment were removed from the composition of thematerial A for a glaze (for the monovalent metal component, the totalweight of K₂O and Na₂O, was 3.6% by weight based on the total weight ofthe glass component; the content of Li₂O component=0% by weight). Thismaterial for a glaze was melted at 1300 to 1400° C. in an electricfurnace, and the melt was then quenched in water to obtain a glass frit.The glass frit was then stamp milled to obtain a powder. The powder thusobtained (600 g), 400 g of water, and 1 kg of alumina balls were placedin a ceramic pot having a volume of 2 liters, and the mixture was thenball milled for about 18 hr. Thus, a glaze slurry as a glaze N wasobtained. The particle diameter of the glaze N was measured with a laserdiffraction particle size distribution analyzer. As a result, it wasfound that 68% of the particles were accounted for by particles having adiameter of not more than 10 μm and the 50% average particle diameter(D50) was 6.0 μm.

Next, the glaze J was spray coated onto the same plate specimen as usedin Example A1 to form a first glaze layer. The glaze N was then spraycoated on the first glaze layer to form a second glaze layer.Thereafter, the glaze M was then spray coated on the second glaze layerto form a third glaze layer. The plate specimen thus obtained was firedat 1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1, 2 and 4 to 6 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.06 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −72.0 mV.

Test 4: Forty five sec after the submergence, the oil film wassubstantially completely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Example C4

The same plate specimen as used in Example A1 was prepared. The glaze Jas used in Example C1 was spray coated onto the plate specimen to form alower glaze layer. The glaze N as used in Example C3 was then spraycoated onto the lower glaze layer to from an upper glaze layer. Further,1.0 g of an aqueous sodium carbonate solution (concentration 10%) wassprayed thereon, followed by firing at 1100 to 1200° C. to obtain asample.

For the sample thus obtained, tests 1, 2 and 4 to 6 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.04 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −68.8 mV.

Test 4: Sixty sec after the submergence, the oil film was substantiallycompletely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Example 5

Sodium carbonate, potassium carbonate, and lithium carbonate powderswere added to the glaze slurry N prepared in Example C3, and the mixturewas stirred for about one hr (f or the monovalent metal component, thetotal weight of K₂O and Na₂O=7.2% by weight based on the total weight ofthe glass component; the content of Li₂O component=0.7% by weight).Thus, a glaze slurry as a glaze O was obtained. The particle diameter ofthe glaze O was measured with a laser diffraction particle sizedistribution analyzer. As a result, it was found that 68% of theparticles were accounted for by particles having a diameter of not morethan 10 μm and the 50% average particle diameter (D50) was 6.0 μm.

Next, the glaze J was spray coated onto the same plate specimen as usedin Example A1 to form a lower glaze layer, and the glaze O was spraycoated thereon to form an upper glaze layer, followed by firing at 1100to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1, 2 and 4 to 6 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.04 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −63.2 mV.

Test 4: Fifty sec after the submergence, the oil film was substantiallycompletely separated from the glaze surface.

Test 5: The oil stain created by dropping the oil on the surface of theglaze layer was substantially completely run down, although a very smallamount of oil droplets were present on the surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Comparative Example C1

The glaze J was spray coated onto the same plate specimen as used inExample A1, followed by firing at 1100 to 1200° C. to obtain a sample.

For the sample thus obtained, tests 1, 2 and 4 to 7 described above werecarried out. The results were as follows.

Test 1: The surface roughness of the glaze layer as the outermost layerwas Ra=0.10 μm.

Test 2: The zeta potential of the glaze layer as the outermost layer inits surface was −51.5 mV.

Test 4: Even 5 min after the submergence, the oil film still stayed on apart of the glaze surface.

Test 5: A wide oil film stayed in a belt in the vertical direction ofthe surface of the glaze layer.

Test 6: The glaze layer had a satisfactory appearance, that is, whenvisually inspected, was free from any defect, such as cracks, and didnot suffer from any problem as a sanitary ware.

Test 7: A reflection electron composition image and a mapping image onthe surface of the glaze layer are shown in FIG. 10. As can be seen fromFIG. 10, ZrO₂ as the opacifier and silica particles remainingundissolved were present in a dispersed state on the whole surface ofthe glaze layer, and builder components (for example, sodium andpotassium) were absent on portions where the opacifier and the silicaparticles were present. This suggests that ZrO₂ as the opacifier and thesilica particles remaining undissolved inhibited the release of buildercomponents (for example, sodium and potassium) on the surface of thelayer.

The evaluation results of Examples C1 to C5 and Comparative Example C1are summarized in Table 4.

TABLE 4 Appearance Stain resistance test Stain resistance test (visualinspection) In water In air Zeta potential Example C1 A 35 sec A −68.3mV Example C2 A 30 sec A −66.5 mV Example C3 A 35 sec A −72.0 mV ExampleC4 A 60 sec A −68.8 mV Example C5 A 50 sec A −63.2 mV Comparative AUnseparable C −57.2 mV Example C1 Reference) Zeta potential of E. coliat pH 7: −41 mV Note) “Evaluation of appearance” A: There was no defecton the surface of the glaze layer. B: There was a defect on a part ofthe surface of the glaze layer. C: There was a defect on the wholesurface of the glaze layer. “Stain resistance test (in air)” A: The oilfilm was substantially completely run down. B: A part of the oil filmstayed on the plate specimen. C: The oil film in its large part stayedon the plate specimen.

What is claimed is:
 1. A sanitary ware comprising a sanitary ware bodyand a glaze layer as an outermost layer of the sanitary ware; the glazelayer as the outermost layer is substantially free from opacifiersand/or pigments or, alternatively, an average particle diameter ofparticles which comprise the glaze layer as the outermost layer is notmore than 6.0 μm if the glaze layer as the outermost layer containsopacifiers and/or pigments; and the surface of the glaze layer as theoutermost layer has a surface roughness Ra of less than 0.07 μm asmeasured with a stylus type surface roughness tester according to JIS B0651 (1996), furthermore; the content, as measured by X-rayphotoelectron spectroscopy from the surface of the outermost layer, of amonovalent metal component and/or a metal component having a measure ofthe electronegativity based on Pouling's rule of not more than 1 in theglaze layer as the outermost layer is less than 20% by weight in termsof oxide based on the whole metal component in the glaze layer as theoutermost layer; wherein the metal component is releasable evenly andcontinuously, over the whole surface of the glaze layer as the outermostlayer, in an amount effective to impart a self-cleaning function forreleasing stains or soils to the surface of the glaze layer as theoutermost layer, and the metal component is supplied from the glazelayer as the outermost layer and/or the sanitary ware body to the wholesurface of the glaze layer as the outermost layer.
 2. The sanitary wareaccording to claim 1 wherein the zeta potential at pH 7 of the surfaceof the glaze layer as the outermost layer is negative and has anabsolute value of not less than 60 mV.
 3. The sanitary ware according toclaims 1 or 2 wherein the metal component is contained in at least thesanitary ware body.
 4. The sanitary ware according to claim 3, whereinthe metal component is contained in the glaze layer as the outermostlayer and the sanitary ware body.
 5. The sanitary ware according toclaim 1, wherein, as measured by X-ray photoelectron spectroscopy fromthe surface of the outermost layer, the content of the metal componentin the glaze layer as the outermost layer is not less than 7% by weightin terms of oxide based on the whole metal component in the glaze layeras the outermost layer.
 6. The sanitary ware according to claim 1,wherein the content of the metal component in the sanitary ware body isnot less than 5% by weight in terms of oxide based on the whole metalcomponent in the sanitary ware body.
 7. The sanitary ware according toclaim 1, wherein the glaze layer as the outermost layer consistsessentially of an amorphous component.
 8. The sanitary ware according toclaim 1, wherein the glaze layer as the outermost layer consistsessentially of a hydratable material.
 9. The sanitary ware according toclaim 1, wherein the glaze layer as the outermost layer furthercomprises an antimicrobial metal.
 10. The sanitary ware according toclaim 1, wherein the antimicrobial metal is silver and/or copper and, asmeasured by X-ray photoelectron spectroscopy from the surface of theglaze layer as the outermost layer, the content of the antimicrobialmetal in the glaze layer as the outermost layer is not less than 0.1% byweight in terms of oxide based on the whole metal component.
 11. Asanitary ware comprising a sanitary ware body and a glaze layer as anoutermost layer of the sanitary ware; the glaze layer as the outermostlayer is a transparent glaze layer which is substantially free from theopacifiers and/or pigments, and the sanitary ware further comprises acolored glaze layer as an intermediate layer provided between thesanitary ware body and the glaze layer as the outermost layer, and thesurface of the glaze layer as the outermost layer has a surfaceroughness Ra of less than 0.07 μm as measured with a stylus type surfaceroughness tester according to JIS B 0651 (1996), furthermore; thecontent, as measured by X-ray photoelectron spectroscopy from thesurface of the outermost layer, of a monovalent metal component and/or ametal component having a measure of the electronegatively based onPouling's rule of not more than 1 in the glaze layer as the outermostlayer is less than 30% by weight in terms of oxide based on the wholemetal component in the glaze layer as the outermost layer; wherein themetal component is releasable evenly and continuously, over the wholesurface of the glaze layer as the outermost layer, in an amounteffective to impart a self-cleaning function for releasing stains orsoils to the surface of the glaze layer as the outermost layer, and themetal component is supplied from the glaze layer as the outermost layerand/or the sanitary ware body to the whole surface of the glaze layer asthe outermost layer.
 12. The sanitary ware according to claim 11,wherein the zeta potential of the surface of the glaze layer as theoutermost layer at pH 7 is negative and has an absolute value of notless than 60 mV.
 13. The sanitary ware according to claim 11 or 12,wherein the metal component is contained in at least the glaze layer asthe outermost layer.
 14. The sanitary ware according to claim 11,wherein the metal component is contained in the sanitary ware body andthe glaze layer as the intermediate layer.
 15. The sanitary wareaccording to claim 11, wherein, as measured by X-ray photoelectronspectroscopy from the surface of the glaze layer as the outermost layer,the content of the metal component in the glaze layer as the outermostlayer is not less than 7% by weight in terms of oxide based on the wholemetal component in the glaze layer as the outermost layer.
 16. Thesanitary ware according to claim 11, wherein the content of the metalcomponent in the sanitary ware body is not less than 5% by weight interms of oxide based on the whole metal component in the sanitary warebody.
 17. The sanitary ware according to claim 11, wherein the glazelayer as the outermost layer consists essentially of an amorphouscomponent.
 18. The sanitary ware according to claim 11, wherein theglaze layer as the outermost layer consists essentially of a hydratablematerial.
 19. The sanitary ware according to claim 11, wherein the glazelayer as the outermost layer further comprises an antimicrobial metal.20. The sanitary ware according to claim 11, wherein the antimicrobialmetal is silver and/or copper and, as measured by X-ray photoelectronspectroscopy from the surface of the glaze layer as the outermost layer,the content of the antimicrobial metal in the glaze layer as theoutermost layer is not less than 0.1% by weight in terms of oxide basedon the whole metal component.
 21. A sanitary ware comprising a sanitaryware body and a glaze layer as an outermost layer of the sanitary ware;the sanitary ware further comprises a metal component layer whichcomprises the metal component as a main component, between the sanitaryware body and the glaze layer as the outermost layer; the glaze layer asthe outermost layer is substantially free from opacifiers and/orpigments or, alternatively, an average particle diameter of particleswhich comprise the glaze layer as the outermost layer is not more than6.0 μm if the glaze layer as the outermost layer contains opacifiersand/or pigments, and the surface of the glaze layer as the outermostlayer has a surface roughness Ra of less than 0.07 μm as measured with astylus type surface roughness tester according to JIS B 0651 (1996);whereby the metal component is provided so as to be releasable evenlyand continuously, over the whole surface of the glaze layer as theoutermost layer, in such an amount large enough to impart aself-cleaning function for releasing stains or soils to the surface ofthe glaze layer as the outermost layer, and the metal component issuppliable from the glaze layer as the outermost layer and/or thesanitary ware body and the metal component layer to the whole surface ofthe glaze layer as the outermost layer.
 22. The sanitary ware accordingto claim 21, wherein the zeta potential at pH 7 of the surface of theglaze as the outermost layer is negative and has an absolute valve ofnot less than 60 mV.
 23. The sanitary ware according to claim 21 or 22,wherein the glaze layer as the outermost layer consists essentially ofan amorphous component.
 24. The sanitary ware according to claim 21,wherein the glaze layer as the outermost layer consists essentially of ahydratable material.
 25. The sanitary ware according to claim 21,wherein the glaze layer as the outermost layer further comprises anantimicrobial metal.
 26. The sanitary ware according to claim 25,wherein the antimicrobial metal is silver and/or copper and, as measuredby X-ray photoelectron spectroscopy from the surface of the glaze layeras the outermost layer, the content of the antimicrobial metal in theglaze layer as the outermost layer is not less than 0.1% by weight interms of oxide based on the whole metal component.
 27. A sanitary warecomprising a sanitary ware body and a glaze layer as an outermost layerof the sanitary ware; the glaze layer as the outermost layer is atransparent glaze layer which is substantially free from opacifiersand/or pigments; the sanitary ware further comprises, provided betweenthe sanitary ware body and the glaze layer as the outermost layer, acolored glaze layer as an intermediate layer provided on the sanitaryware body side and metal component layer which comprises the metalcomponent as a main component, provided on the side of the glass layeras the outermost layer, and the surface of the glaze layer as theoutermost layer has a surface roughness Ra of less than 0.07 μm asmeasured with a stylus type surface roughness tester according to JIS B0651 (1996); whereby the metal component is provided so as to bereleasable evenly and continuously, over the whole surface of the glazelayer as the outermost layer, in such an amount large enough to impart aself-cleaning function for releasing stains or soils to the surface ofthe glaze layer as the outermost layer, and the metal component issuppliable from the glaze layer as the outermost layer and/or thesanitary ware body and the metal component layer to the whole surface ofthe glaze layer as the outermost layer.
 28. The sanitary ware accordingto claim 27, wherein the zeta potential at pH 7 of the surface of theglaze layer as the outermost layer is negative and has an absolute valueof not less than 60 mV.
 29. The sanitary ware according to claim 27 or28, wherein the glaze layer as the outermost layer consists essentiallyof an amorphous component.
 30. The sanitary ware according to claim 27,wherein the glaze layer as the outermost layer consists essentially of ahydratable material.
 31. The sanitary ware according to claim 27,wherein the glaze layer as the outermost layer further comprises anantimicrobial metal.
 32. The sanitary ware according to claim 31,wherein the antimicrobial metal is silver and/or copper and, as measuredby X-ray photoelectron spectroscopy from the surface of the glaze layeras the outermost layer, the content of the antimicrobial metal in theglaze layer as the outermost layer is not less than 0.1% by weight interms of oxide based on the whole metal component.
 33. A sanitary warecomprising a sanitary ware body and a glaze layer as an outermost layerof the sanitary ware; the sanitary ware further comprises, providedbetween the sanitary ware body and the glaze layer as the outermostlayer, a metal component layer which comprises the metal component as amain component, provided on the sanitary ware body side and a coloredglaze layer as an intermediate layer provided on the side of the glazelayer as the outermost layer; the glaze layer as the outermost layer isa transparent glaze layer which is substantially free from opacifiersand/or pigments, and the surface of the glaze layer as the outermostlayer has a surface roughness Ra of less than 0.07 μm as measured with astylus type surface roughness tester according to JIS B 0651 (1996);whereby the metal component is provided so as to be releasable evenlyand continuously, over the whole surface of the glaze layer as theoutermost layer, in such an amount large enough to impart aself-cleaning function for releasing stains or soils to the surface ofthe glaze layer as the outermost layer, and the metal component issuppliable from the glaze layer as the outermost layer and/or thesanitary ware body and the metal component layer to the whole surface ofthe glaze layer as the outermost layer.
 34. The sanitary ware accordingto claim 33, wherein the zeta potential at pH 7 of the surface of theglaze layer as the outermost layer is negative and has an absolute valueof not less than 60 mV.
 35. The sanitary ware according to claim 33 or34, wherein the glaze layer as the outermost layer consists essentiallyof an amorphous component.
 36. The sanitary ware according to claim 33,wherein the glaze layer as the outermost layer consists essentially of ahydratable material.
 37. The sanitary ware according to claim 33,wherein the glaze layer as the outermost layer further comprises anantimicrobial metal.
 38. The sanitary ware according to claim 37,wherein the antimicrobial metal is silver and/or copper and, as measuredby X-ray photoelectron spectroscopy from the surface of the glaze layeras the outermost layer, the content of the antimicrobial metal in theglaze layer as the outermost layer is not less than 0.1% by weight interms of oxide based on the whole metal component.
 39. The sanitary wareaccording to any one of claims 1, 11, 21, 27 or 33, which is a toilet ora urinal.
 40. The sanitary ware according to any one of claims 1, 11,21, 27 or 33, which is a washbowl.
 41. The sanitary ware according toany one of claims 1, 11, 21, 27 or 33, which is a strainer for urinals.42. The sanitary ware according to any one of claims 1, 11, 21, 27 or33, which is a toilet.
 43. The sanitary ware according to any one ofclaims 1, 11, 21, 27 or 33, which is a urinal.
 44. The sanitary wareaccording to any one of claims 1, 11, 21, 27 or 33, which is a flushtank for toilets or urinals.
 45. The sanitary ware according to any oneof claims 1, 11, 21, 27 or 33, which is a wash hand basin.
 46. Asanitary ware comprising: a sanitary ware body; a glaze layer as anoutermost layer of the sanitary ware; and a metal component layer,comprising the metal component as a main component, provided between thesanitary ware body and the outermost layer.
 47. The sanitary ware ofclaim 46 further comprising a colored glaze layer provided between thesanitary ware body and the outermost layer.
 48. The sanitary ware ofclaim 47 wherein the colored glaze layer is provided between thesanitary ware body and the metal component layer.
 49. The sanitary wareof claim 47 wherein the colored glaze layer is provided between theoutermost glaze layer and the metal component layer.